Use of partially fluorinated polymers in applications requiring transparency in the ultraviolet and vacuum ultraviolet

ABSTRACT

Disclosed are partially fluorinated and fully fluorinated polymers that are substantially transparent to ultraviolet radiation at wavelengths from approximately 150 nanometer to 260 nanometers.

FIELD OF THE INVENTION

The present invention provides methods and associated apparatus fortransmission of light in the range of 150 to 260 nanometers (nm),especially at 157 nm, 193 nm, and 248 nm, utilizing partiallyfluorinated polymers exhibiting high transparency.

TECHNICAL BACKGROUND OF THE INVENTION

The semiconductor industry is the foundation of the trillion dollarelectronics industry. The semiconductor industry continues to meet thedemands of Moore's law, whereby integrated circuit density doubles every18 months, in large part because of continuous improvement of opticallithography's ability to print smaller features on silicon. This in turndepends in part upon identifying materials which exhibit sufficienttransparency for practical use at ever-shorter wavelengths. For example,in photolithography, a circuit pattern is represented in a photomask,and an optical stepper is used to project the mask pattern onto aphotoresist layer on a silicon wafer. Currently commercial scalephotolithography is done at 248 nm. Lithography at 193 nm light is justentering early production. Current developmental efforts are directed tophotolithography at 157 nm. A general discussion of photolithographicmethods in electronics and related applications may be found in L. F.Thompson, C. G. Wilson, and M. J. Bowden, editors, Introduction toMicrolithography, Second Edition, American Chemical Society, Washington,D.C. 1994

Polymers play a critical role in lithography in multiple area: one isthe polymer pellicle which is placed over the mask pattern to keep anyparticulate contaminants out of the photomask object plane, therebyensuring that the lithographic imaging will be defect free. The pellicleis a free standing polymer membrane, typically 0.8 micrometers inthickness, which is mounted on a typically 5 inch square frame. Thepellicle film must have high transparency or transmission of light atthe lithographic wavelength for efficient image formation and mustneither darken nor burst with prolonged illumination in the opticalstepper. Typical commercial processes utilize pellicles with >99%transmission through exploitation of polymers with very low opticalabsorption combined with thin film interference effects. The electronicindustry requires greater than 98% transparency over an exposurelifetime of 75 million laser pulses of 0.1 mJ/cm², or a radiation doseof 7.5 kJ/cm².

A pellicle transmission of 98% corresponds to an absorbance A ofapproximately 0.01 per micrometer of film thickness. The absorbance isdefined in Equation 1, where the Absorbance A in units of inversemicrometers (μm⁻¹) is defined as the base 10 logarithm of the ratio ofthe substrate transmission, T_(substrate), divided by the transmissionof the sample, consisting of the polymer film sample on the substrate,T_(sample), divided by the polymer film thickness, t, in micrometers.

$\begin{matrix}{{A_{film}\left( {µm}^{- 1} \right)} = {{A/{um}} = {\frac{{Log}_{10}\left\lfloor {T_{substrate}/T_{sample}} \right\rfloor}{t_{film}}.}}} & {{Equation}\mspace{20mu} 1}\end{matrix}$

Certain perfluoropolymers have been identified in the art as useful foroptical applications such as light guides, anti-reflective coatings andlayers, pellicles, and glues mostly at wavelengths above 200 nm

WO 9836324, Aug. 20, 1998, Mitsui Chemical Inc., discloses the use ofperfluorinated polymers, optionally in combination with siliconepolymers having siloxane backbones, as pellicle membranes having anabsorbance/micrometer of 0.1 to 1.0 at UV wavelengths from 140 to 200nm.

WO 9822851, May 28, 1998, Mitsui Chemicals, Inc., claims the use at 248nm of low molecular weight photodegradation-resistant, polymericadhesives consisting largely of —(CF₂-CXR) copolymers in which X ishalogen and R is —Cl or —CF₃. Higher molecular weight polymers such aspoly(perfluorobutenyl vinyl ether),poly[(tetrafluoroethylene/perfluoro-(2,2-dimethyl-1,3-dioxole)],

poly(tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride),

poly(hexafluoropropylene/vinylidene fluoride), or poly(chlorotolyl

fluorethylene/vinylidene fluoride) are disclosed as minor components toimprove creep resistance. Only poly(chlorotrifluoroethylene) wasexemplified.

Japanese Patent 07295207, Nov. 10, 1995, Shinetsu Chem. Ind Co, claimsdouble layer pellicles combining Cytop CTXS (poly(CF₂═CFOCF₂CF₂CF═CF₂))with Teflon® AF 1600 for greater strength.

U.S. Pat. No. 5,286,567, Feb.. 15, 1994, Shin-Etsu Chemical Co., Ltd.,claims the use of copolymers of tetrafluoroethylene and five memberedcyclic perfluoroether monomers as pellicles once they have been madehydrophilic, and therefore antistatic, by plasma treatment.

European Patent 416528, Mar. 13, 1991, DuPont, claims amorphousfluoropolymers having a refractive index of 1.24-1.41 as pellicles atwavelengths of 190-820 nm. Copolymers ofperfluoro(2,2-dimethyl-1,3-dioxole) with tetrafluoroethylene,chlorotrifluoroethylene, vinylidene fluoride, hexafluoropropylene,trifluoroethylene, vinyl fluoride, (perfluoroalkyl)ethylenes, andperfluoro(alkyl vinyl ethers) are cited.

Japanese Patent 01241557, Bando Chemical Industries, Ltd., Sep. 26,1989, claims pellicles usable at 280-360 nm using (co)polymers ofvinylidene fluoride (VF₂),

tetrafluoroethylene/hexafluoropropylene (TFE/HFP),

ethylene/tetrafluoroethylene (E/TFE), TFE/CF₂═CFORf,

TFE/HFP/CF₂═CFORf, chlorotrifluoroethylene (CTFE), E/CTFE, CTFE,VF₂ andvinyl fluoride (VF).

Japanese Patent 59048766, Mar. 21, 1984, Mitsui Toatsu Chemicals, Inc.,claims the use of a stretched film of poly(vinylidene fluoride) ashaving good transparency from 200 to 400 nm.

French et al, WO0137044, discloses vacuum ultraviolet (VUV) transparentmaterials exhibiting an absorbance/micron (A/micrometer) ≦1 atwavelengths from 140-186 nm comprising amorphous vinyl homopolymers ofperfluoro-2,2-dimethyl-1,3-dioxole or CX₂═CY₂, where X is —F or —CF₃ andY is H, or amorphous vinyl copolymers ofperfluoro-2,2-dimethyl-1,3-dioxole and CX₂═CY₂.

French et al, WO0137043 discloses ultraviolet transparent materialsexhibiting an absorbance/micron (A/micrometer) ≦1 at wavelength from187-260 nm comprising amorphous vinyl copolymers of CX₂═CY₂, wherein Xis —F or —CF₃ and Y is H and 0 to 25 mole % of one or more monomersCRaRb═CRcRd in the case where the CRaRb═CRcRd enters the copolymer inapproximately alternating fashion, or 40 to 60 mole % of one or moremonomers CRaRb═CrcRd in the case where the CRaRb═CrcRd enters thecopolymer in approximately alternating fashion where each of Ra, Rb, andRc is selected independently from H or F and where Rd is selected fromthe group consisting of —F, —CF₃, —ORf where Rf is CnF_(2n+1) with n=1to 3, —OH (when Rc═H), and Cl (when Ra, Rb, and Rc═F).

Japanese Patent Application Kokai Number P2000-305255A Shin-EtsuChemical Company discloses copolymers containing >70%perfluorodimethyldioxole and 0-30 mole % tetrafluoroethylene,trifluoroethylene, difluoroethylene, vinylidene fluoride, andhexafluoropropylene for use as pellicles at 158 nm.

Japanese Patent Publication P2000-338650AShin-Etsu Chemical Companydiscloses copolymers containing >20% of perfluoroalkoxy substituteddioxoles such as 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole withF-containing radically polymerizing monomers such astetrafluoroethylene, trifluoroethylene, difluoroethylene, vinylidenefluoride, and hexafluoropropylene for use as pellicles at 157 nm.

U.S. patent publication 20010024701 from Asahi Glass Company disclosesfluorine containing polymers having a polymer chain consisting of carbonatoms wherein some chain carbons are substituted with fluorine andunspecified fluorine-containing groups. Encompassed in the disclosureare numerous polymers which are unsuitable in practice for use inapplications at 157 nm because they are strongly absorbing or highlycrystalline with concomitant high light scattering. Pellicles areinoperable without reasonably high transparency and yet the claims aswritten could include 100% opaque materials and fails to teach anymethod by which highly useful and completely useless polymer candidatesfor such applications can be distinguished from one another.

Many of the fluoropolymers cited in the references above are noticeablyhazy to the eye because of crystallinity and are therefore unsuitablefor applications requiring high light transmission and the projection ofprecision circuit patterns. Poly(vinylidene fluoride),poly(chlorotrifluoroethylene), poly(tetrafluoroethylene/ethylene),commercially available poly(tetrafluoroethylene/hexafluoropropylene)compositions, and poly(ethylene/chlorotrifluoroethylene) are all suchcrystalline, optically hazy materials. More recent references have thusbeen directed at amorphous perfluoropolymers such as Cytop® and Teflon®AF because they combine outstanding optical clarity down to at least 193nm, solubility, and a complete lack of crystallinity.

Absorption maxima for selected hydrocarbon and fluorocarbon compoundsare shown in Table 1. For hydrocarbons H(CH₂)_(n)H the data for n=1-8 iscited in B. A. Lombos et al Chem. Phys. Lett., 1967, 42. Forfluorocarbons F(CF2)nF the n=3-6 data is cited in G. Belanger et. al.,Chem. Phys. Letters, 3, 649(1969) while the datum for n=172 is cited inK. Sekl et al, Phys. Scripta, 41, 167(1990).

TABLE 1 Comparison of UV Absorption Maxima for Hydrocarbons andFluorocarbons WAVELENGTH OF ABSORPTION MAXIMUM C_(n)H_(2n+2)C_(n)F_(2n+2) n = 1 143 nm & 128 nm n = 2 158 nm & 132 nm n = 3 159 nm &140 nm 119 nm n = 4 160 nm & 141 nm 126 nm n = 5 161 nm & 142 nm 135 nmn = 6 162 nm & 143 nm 142 nm n = 7 163 nm & 143 nm n = 8 163 nm & 142 nmn = 172 161 nm

As can be seen from the table, UV absorption maxima move to longerwavelengths as chain length increases for both hydrocarbons andfluorocarbons. Perfluorocarbon chains (CF₂)_(n) absorb at 157 nmsomewhere between n=6 (142 nm) and n=172 (161 nm) while hydrocarbonchains (CH₂)_(n) absorb at 157 nm perhaps as early as n=2. But, as longas chain lengths offering acceptable transparency are limited to (CH₂)or (CH₂)₆, perfectly transparent polymers at 157 nm and somewhat longerwavelengths would seem precluded according to the known art. Consistentwith this, V. N. Vasilets, et al., J. Poly. Sci, Part A, Poly. Chem.,36, 2215(1998) for example report that various compositions ofpoly(tetrafluoroethylene/hexafluoropropylene) show strong absorption andphotochemical degradation at 147 nm. Similarly the inventors hereof havefound that 1:1 poly(hexafluoropropylene:tetrafluoroethylene) is highlyabsorbing at 157 nm

The absorbance per micron of a polymer will determine the averagetransmission of an unsupported pellicle film made from that polymer. Forany particular polymer, the pellicle transmission can be increased,through the use of a thinner pellicle film thickness. This approach toincreasing the pellicle transmission has a limited range of utility,since the pellicle film must have sufficient mechanical strength andintegrity. These mechanical requirements suggest the use of polymer withrelatively high glass transition temperature Tg and polymer filmthicknesses of 0.6 microns or greater.

SUMMARY OF THE INVENTION

This invention provides a method comprising causing a source to emitelectromagnetic radiation in the wavelength range from 150 nanometers to260 nanometers; disposing a target surface in the path of at least aportion of said electromagnetic radiation in such a manner that at leasta portion of said target surface will be thereby illuminated; andinterposing in the path of at least a portion of said electromagneticradiation between said target surface and said source a shaped articlecomprising a fluoropolymer exhibiting an absorbance/micrometer ≦1 atwavelengths in the range of 150 to 260 nm and a heat of fusion of <1 J/gsaid fluoropolymer being a homopolymer selected from group A orcopolymers from groups B, C, and D wherein

-   -   group A consists of the homopolymer of CH₂═CFCF₃    -   group B consists of copolymers comprising >25 mole % of monomer        units derived from CF₂═CHOR_(f) in combination with monomer        units derived from vinylidene fluoride wherein R_(f) is a linear        or branched C1 to C6 fluoroalkyl radical having the formula        C_(n)F_(2n−y+1)Hy wherein the number of hydrogens is less than        or equal to the number of fluorines, no more than two adjacent        carbons atoms are bonded to hydrogens, and either oxygen can        replace one or more of the carbons providing at least one of the        carbons adjacent to any ether oxygen is perfluorinated;    -   group C consists of copolymers comprising >10 mole % of monomer        units derived from CH₂═CFCF₃, CF₂═CHOR_(f), or a mixture thereof        in combination with monomer unit derived from 1,3        perfluorodioxoles wherein R_(f) is a linear or branched C1 to C6        fluoroalkyl radical having the formula C_(n)F_(2n−y+1)Hy wherein        the number of hydrogens is less than or equal to the number of        fluorines, no more than two adjacent carbon atoms are bonded to        hydrogens, and ether oxygen can replace one or more of the        carbons providing at least one of the carbons adjacent to any        oxygen is perfluorinated, and wherein said 1,3-perfluorodioxole        has the structure

wherein R_(a) and R_(b) are independently F or linear —C_(n)F_(2n+1),optionally substituted by ether oxygen, for which n=1 to 5.

group D consists of copolymers comprising 40 to 60 mole % of monomerunits derived from a monomer represented by the formula

in combination with monomer units derived from vinylidene fluoride andor vinyl fluoride wherein G and Q are independently F (but not both F),H, R_(f), or —OR_(f) wherein R_(f) is a linear or branched C1 to C5fluoroalkyl radical having the formula C_(n)F_(2n−y+1)H_(y) wherein thenumber of hydrogens is less than or equal to the number of fluorines, nomore than two adjacent carbons atoms are bonded to hydrogens, and etheroxygen can replace one or more of the carbons providing that at leastone of the carbons adjacent to any ether oxygen is perfluorinated.

Further provided in the present invention is an apparatus comprising anactivateable source of electromagnetic radiation in the wavelength rangeof 150-260 nanometers; and a shaped article comprising a fluoropolymerexhibiting an absorbance/micron ≦1 at wavelengths from 150 to 260 nm anda heat of fusion of <1 J/g said fluoropolymer being a homopolymerselected from group A or copolymers from groups B, C, and D wherein

-   -   group A consists of the homopolymer of CH₂═CFCF₃    -   group B consists of copolymers comprising >25 mole % of monomer        units derived from CF₂═CHOR_(f) in combination with monomer        units derived from vinylidene fluoride wherein R_(f) is a linear        or branched C1 to C6 fluoroalkyl radical having the formula        C_(n)F_(2n−y+1)H_(y) wherein the number of hydrogens is less        then or equal to the number of fluorines, no more than two        adjacent carbons atoms are bonded to hydrogens, and ether oxygen        can replace one or more of the carbons providing at least one of        the carbons adjacent to any ether oxygen is perfluorinated;    -   group C consists of copolymers comprising >10 mole % of monomer        units derived from CH₂═CFCF₃, CF₂═CHOR_(f), or a mixture thereof        in combination with monomer unit derived from 1,3        perfluorodioxoles wherein R_(f) is a linear or branched C1 to C6        fluoroalkyl radical having the formula C_(n)F_(2n−y+1)H_(y)        wherein the number of hydrogens is less than or equal to the        number of fluorines, no more than two adjacent carbons atoms are        bonded to hydrogens, and ether oxygen can replace one or more of        the carbons providing at least one of the carbons adjacent to        any oxygen is perfluorinated, and wherein said        1,3-perfluorodioxole has the structure

wherein R_(a) and R_(b) are independently F or linear —C_(n)F_(2n+1),optionally substituted with ether oxygen, for which n=1 to 5.

-   -   group D consists of copolymers comprising 40 to 60 mole % of        monomer units derived from a monomer represented by the formula

in combination with monomer units derived from vinylidene fluoride andor vinyl fluoride wherein G and Q are independently F (but not both F),H, R_(f), or —OR_(f) wherein R_(f) is a linear or branched C1 to C5fluoroalkyl radical having the formula C_(n)F_(2n−y+1)H_(y) wherein thenumber of hydrogens is less than or equal to the number of fluorines, nomore than two adjacent carbons atoms are bonded to hydrogens, and etheroxygen can replace one or more of the carbons providing that at leastone of the carbons adjacent to any ether oxygen is perfluorinated;said shaped article being disposed to lie within the optical path oflight emitted from said source when said source is activated.

This invention further provides pellicles, anti-reflective coatings,optically clear glues, light guides and resists comprising the UVtransparent material described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 describes the absorbance in units of inverse micrometers versuswavelength lambda (λ) in units of nanometers for the polymer of Example1 (Poly[(CH₂═C(CF₃)CF₂OCH(CF₃)₂/CH₂═CF₂).

FIG. 2 describes the index of refraction (n) versus wavelength lambda(λ), in units of nanometers for the polymer of Example 1.

FIG. 3 describes the absorbance in units of inverse micrometers versuswavelength lambda (λ) in units of nanometers for the polymer of Example2 (Poly[(CH₂═C(CF₃)CF₂OCF(CF₃)₂/CH₂═CF₂).

FIG. 4 describes the index of refraction (n) versus wavelength lambda(λ) in units of nanometers for the polymer of example 2(Poly[(CH₂═C(CF₃)CF₂OCF(CF₃)₂/CH₂═CF₂).

FIG. 5 describes the absorbance in units of inverse micrometers versuswavelength lambda (λ) in units of nanometers for the polymer of example3 (Poly(CF₂═CHOCF₂CF₂H/CH₂═CF₂).

FIG. 6 describes the index of refraction (n) versus wavelength lambda(λ) in units of nanometers, for the polymer of example 3(Poly(CF₂═CHOCF₂CF₂H/CH₂═CF₂)).

DETAILED DESCRIPTION OF THE INVENTION

The method of the present invention has several embodiments, all relatedto the use of electromagnetic radiation in the range of 150 nm to 260 nmfor illuminating a surface. In a preferred embodiment of the method ofthe invention, the method is applied in the area of photolithographicprocesses for the fabrication of circuit elements in electronics asdescribed hereinabove and in the references cited. In other embodiments,the method may be applied to vacuum ultraviolet spectroscopy, or inmicroscopy. Since the novelty of the method lies in the use of polymericmaterials heretofore unknown to be useful for transmittingelectromagnetic radiation in the wavelength region from 150 nm-260 nm inthere is no limitation on the number of potential embodiments just solong as the elements of the present method are applied.

In the method of the invention, a source of electromagnetic radiationsuch as a lamp (such as a mercury or mercury-xenon lamp, a deuteriumlamp or other gas discharge lamp of either the sealed or flowing gastype), an excimer lamp such as produces 172 nm radiation or otherlamps), a laser (such as the excimer gas discharge lasers which produce248 nm electromagnetic radiation from KrF gas, 193 nm radiation from ArFgas or 157 nm from F2 gas, or frequency up converted as by non linearoptical processes of laser whose emission in in the ultraviolet, visibleor infrared), a black body light source at a temperature of at least2000 degrees kelvin. An example of such a black body light source beinga laser plasma light source where by a high powered laser is focused toa small size onto a metal, ceramic or gas target, and a plasma is formedas for example in the samarium laser plasma light source whereby a blackbody temperature on the order of 250,000 degrees Kelvin is achieved, andblack body radiation from the infrared to the x-ray region can beproduced, LPLS light sources which emits radiation in the wavelengthrange from 150 nm to 260 nm are discussed in greater detail in R. H.French, “Laser-Plasma Sourced, Temperature Dependent VUVSpectrophotometer Using Dispensive Analysis”, Physica Scripta, 41, 4,404-8, (1990)). In a preferred embodiment, the source is an excimer gasdischarge laser emitting at 157 nm, 193 nm, or 248 nm, most preferably,157 nm.

At least a portion of the light emitted from the source is directed to atarget surface at least a portion of which will be illuminated by theincident light. In a preferred embodiment, the target surface is to be aphotopolymer surface which undergoes light-induced chemical reaction inresponse the incidence of the radiation. Clariant has just introduced a157 nm fluoropolymer resist under the name AZ EXP FX 1000P which islikely a hydrofluorocarbon polymer incorporating ring structures foretch stability and protected fluoroalcohol groups for aqueous basesolubility.

In the process for manufacturing semiconductor devices, very finefeatures are etched onto a substrate, typically a silicon wafer. Thefeatures are formed on the substrate by electromagnetic radiation whichis impinged, imagewise, on a photoresist composition applied to thesilicon wafer. Areas of the photoresist composition which are exposed tothe electromagnetic radiation change chemically and/or physically toform a latent image which can be processed into an image forsemiconductor device fabrication. Positive working photoresistcompositions generally are utilized for semiconductor devicemanufacture.

The photoresist composition typically is applied to the silicon wafer byspin coating. The silicon wafer may have various other layers applied toit in additional processing steps. Examples of such additional layerssuch as are known in the art include but are not limited to a hard masklayer, typically of silicon dioxide or silicon nitride, and anantireflective layer. Typically the thickness of the resist layer issufficient to resist the dry chemical etch processes used intransferring a pattern to the silicon wafer.

A photoresist is typically comprised of a polymer and at least onephotoactive component. The photoresists can either be positive-workingor negative-working. Positive-working photoresists are preferred. Thesephotoresists can optionally comprise dissolution inhibitors and/or otheradditional components such as are commonly employed in the art. Examplesof additional components include but are not limited to, resolutionenhancers, adhesion promoters, residue reducers, coating aids,plasticizers, and T_(g) (glass transition temperature) modifiers.

Various polymer products for photoresist compositions have beendescribed in Introduction to Microlithography, Second Edition by L. F.Thompson, C. G. Willson, and M. J. Bowden, American Chemical Society,Washington, D. C., 1994.

The photoresist composition generally comprises a film forming polymerwhich may be photoactive and a photosensitive composition that containsone or more photoactive components. Upon exposure to electromagneticradiation (e.g., UV light), the photoactive component acts to change therheological state, solubility, surface characteristics, refractiveindex, color, optical characteristics or other such physical or chemicalcharacteristics of the photoresist composition.

Shorter wavelengths correspond to higher resolution.

Imagewise Exposure

The photoresist compositions suitable for use in the process of theinstant invention are sensitive in the ultraviolet region of theelectromagnetic spectrum and especially to those wavelengths ≦365 nm.Imagewise exposure of the resist compositions of this invention can bedone at many different UV wavelengths including, but not limited to, 365nm, 248 nm, 193 nm, 157 nm, and lower wavelengths. Imagewise exposure ispreferably done with ultraviolet light of 248 nm, 193 nm, 157 nm, orlower wavelengths, more preferably it is done with ultraviolet light of193 nm, 157 nm, or lower wavelengths, and most preferably, it is donewith ultraviolet light of 157 nm or lower wavelengths. Imagewiseexposure can either be done digitally with a laser or equivalent deviceor non-digitally with use of a photomask. Suitable laser devices forimaging of the compositions of this invention include, but are notlimited to, an argon-fluorine excimer laser with UV output at 193 nm, akrypton-fluorine excimer laser with UV output at 248 nm, and a fluorine(F2) laser with output at 157 nm. These excimer lasers could be used fordigital imaging, but thy are also the basis for non-digital imagingusing photomasks in optical steppers. Optical steppers for 248 nm canuse lamps or KrF excimer laser light sources, and at 193 and 157 nm thelight source is an excimer laser, 193 nm=ArF and 157 nm=F2 excimerlaser. Since, as discussed supra, use of UV light of lower wavelengthfor imagewise exposure corresponds to higher resolution the use of alower wavelength (e.g., 193 nm or 157 nm or lower) is generallypreferred over use of a higher wavelength (e.g., 248 nm or higher).

Development

The polymers suitable for use in the present invention can be formulatedas a positive resist wherein the areas exposed to UV light becomesufficiently acidic to be selectively washed out with aqueous base.Sufficient acidity is imparted to the copolymers by acid or protectedacid (which can be 100% in protected form prior to exposure provideddeprotection occurs during exposure to afford sufficient free acid toprovide for development) such that aqueous development is possible usinga basic developer such as sodium hydroxide solution, potassium hydroxidesolution, or tetramethylammonium hydroxide solution. In this invention,a given copolymer for aqueous processability (aqueous development) inuse is typically a carboxylic acid-containing and/orfluoroalcohol-containing copolymer (after exposure) containing at leastone free carboxylic acid group and/or fluoroalcohol group. The level ofacid groups (e.g., free carboxylic acid or fluoroalcohol groups) isdetermined for a given composition by optimizing the amount needed forgood development in aqueous alkaline developer.

When an aqueous processible photoresist is coated or otherwise appliedto a substrate and imagewise exposed to UV light, the copolymer of thephotoresist must have sufficient protected acid groups and/orunprotected acid groups so that when exposed to UV the exposedphotoresist will become developable in basic solution. In case of apositive-working photoresist layer, the photoresist layer will beremoved during development in portions which are exposed to UV radiationbut will be substantially unaffected in unexposed portions duringdevelopment by aqueous alkaline liquids such as wholly aqueous solutionscontaining 0.262 N tetramethylammonium hydroxide (with development at25° C. usually for less than or equal to 120 seconds) or 1% sodiumcarbonate by weight (with development at a temperature of 30° C. usuallyfor less than 2 or equal to 2 minutes). In case of a negative-workingphotoresist layer, the photoresist layer will be removed duringdevelopment in portions which are unexposed to UV radiation but will besubstantially unaffected in exposed portions during development usingeither a supercritical fluid or an organic solvent.

Halogenated solvents are preferred and fluorinated solvents are morepreferred.

In a further embodiments, the target surface may be an optical sensorwhich produces an electronic, optical, or chemical signal in response tothe incident radiation such as in the signal or image wise receiver inan optical, electo-optical or electronic detector used in time based,wavelength based or spatially resolved optical communications systems.In these cases the electromagnetic radiation incident on the targetsurface, and its time variation, spatial variation and/or its wavelength(spectral) variations can be used to encode information which can thenbe decoded at the detector. In another embodiment, the target surfacemay be a electro-optical receptor of the type used for light to energyconversion. In another embodiment, the target surface may be a specimenundergoing microscopic examination in the wavelength range of 150-260nm. In yet another embodiment, the target surface may be a luminescentsurface caused to luminesce upon incidence of the 150-260 nm radiationemployed in the method of the invention such as in a imaging system usedas an optical imaging display. In another embodiment, the target surfacemay be a specimen undergoing materials processing, such laser ablation,laser trimming laser melting, laser marking in the wavelength range from150 nm to 260 nm,

According to the method of the invention, a shaped article comprising atransparent, amorphous fluoropolymer as hereinbelow described, isinterposed between the light source and the target. In one embodiment ofthe method of the invention the fluoropolymer of the invention isemployed in an adhesive. In another embodiment of the method, thematerial is employed as a coating or an element to provent theoutgassing under irradiation of dissimilar materials in the system so asto reduce optical contamination by more optically absorbing materials.In another embodiment the adhesivelike material is used as a coating orelement or so as to capture and immobilize particulate contaminants, toavoid their further mitigation and deposition in the system. In anotheremboidment the fluoropolymer is employed as a coating on a non-optical(element (such as a support structure in an optical instrument), anoptical element (such as a mirror, a lens, a beam splitter, a tunedetalon, a detector, a pellicle,). In a further embodiment, thefluoropolymer is itself a shaped article such as a lens or other opticalelement (such as a mirror, a lens, a beam splitter, a tuned etalon, adetector, a pellicle,) or non optical component (such as a supportstructure in an optical instrument). In the most preferred emboidmentthe fluoropolymer is in the form of a pellicle, a free standing membranemounted on a frame (which can be metallic, glass, polymer or othermaterial) which is attached (adhesively or using other methods such asmagnetism) to the surface of a photomask employed in a photolithographicprocess conducted in the wavelength region from 150 nm to 260 nm. Morepreferably, the photolithographic process employs a laser emittingradiation at 157 nm, 193 nm, or 248 nm. Most preferably, thephotolithographic process employs a laser emitting 157 nm radiation.

In the apparatus of the invention is employed an activateable lightsource of the type described hereinabove as suitable for use in themethod of the invention. By “activateable” is meant that the lightsource may be, in conventional terms, “on” or “off” but if in the “off”state may be turned on by conventional means. This light source may alsohave multiple wavelengths (as is used in wavelength divisionmultiplexing in optical communications) through the use of lamps ormultiple lasers of different wavelengths. Thus encompassed within theapparatus of the invention is a light source which may be “off” when sodesired, as when the apparatus is not being used, or is being shipped.However, the light source of the invention can be activated —that is,turned “on”—when it is desired to use it as, for example, in the methodof the present invention. When turned “on” or activated, the lightsource emits electromagnetic radiation in the wavelength range from 150nm-260 nm. Light sources suitable for use in the apparatus of theinvention include a lamp (such as a mercury or mercury-xenon lamp, adeuterium lamp or other gas discharge lamp of either the sealed orflowing gas type), an excimer lamp such as produces 172 nm radiation orother lamps), a laser (such as the excimer gas discharge lasers whichproduce 248 nm electromagnetic radiation from KrF gas, 193 nm radiationfrom ArF gas or 157 nm from F2 gas, or frequency up converted as by nonlinear optical processes of laser whose emission in in the ultraviolet,visible or infrared), a black body light source at a temperature of atleast 2000 degrees Kelvin, an example of such a black body light sourcebeing a laser plasma light source where by a high powered laser isfocused to a small size onto a metal, ceramic or gas target, and aplasma is formed as for example in the samarium laser plasma lightsource whereby a black body temperature on the order of 250,000 degreesKelvin is achieved, and black body radiation from the infrared to thex-ray region can be produced) which emits radiation in the wavelengthrange from 150 nm to 260 nm. In a preferred embodiment, the source is aexcimer gas discharge laser emitting at 157 nm, 193 nm, or 248 nm, mostpreferably, 157 nm.

Further employed in the apparatus of the invention is a shaped articlecomprising the fluoropolymer of the invention, hereinbelow described. Inthe apparatus of the invention, the shaped article is disposed to liewithin the path of electromagnetic radiation emitted from the sourcewhen the source is activated or “turned on.” In one embodiment of theapparatus of the invention the shaped article employs the fluoropolymerof the invention is an adhesive. In another embodiment the fluoropolymeris employed as a coating on an optical or non-optical element. In afurther embodiment, the fluoropolymer is itself formed into a shapedarticle such as a lens or other optical component. In the most preferredembodiment the fluoropolymer is in the form of a pellicle, a protectivefilm typically 0.6 to 1 micron thick that is mounted on a frame that isattached in turn to the surface of a photomask employed in aphotolithographic process conducted in the wavelength region from 150 nmto 260 nm.

While one of skill in the art will appreciate that the method of usecontemplated for the apparatus of the invention necessarily comprises atarget surface of some sort, the apparatus of the invention need notencompass a target surface. For example, the apparatus of the inventioncould be employed as a portable or transportable optical irradiationsystem with a light source and a set of optical components which couldbe used on a variety of target surfaces in several locations.

Pellicle film thickness can be optimized such that the pellicle willexhibit a thin film interference with a maximum in the in thetransmission spectrum at the desired lithographic wavelength. Thespectral transmission maximum of a properly tuned etalon pellicle filmoccurs where the spectral reflectance of the pellicle film exhibits aminimum.

Polymers suitable for the practice of the invention exhibit very lowabsorbance/micron, at least <1, preferably <0.5, more preferably <0.1,and most preferably <0.01. Those which further exhibit values of theindex of refraction which match the index of adjacent optical elementshave important uses antireflective index matching materials andoptically clear index matching adhesives, those which exhibitintermediate values of the index of refraction between those of anoptical element and either the ambient (with an index of 1 for example)or a second adjacent element of a different index of refraction haveimportant applications as anti-reflection coatings and those have a lowvalue of the index of refractions below 1.8, or preferably below 1.6 ormore preferably below 1.45 have very important applications asmultilayer anti-reflection coatings. Such polymers can be used to reducethe light reflected from the surface of a transparent substrate of arelatively higher index of refraction. This decrease in the reflectedlight, leads to a concomitant increase in the light transmitted throughthe transparent substrate material.

The polymers suitable for the practice of the present invention may behomopolymers or copolymers. The suitable homopolymer is selected fromgroup A. Suitable copolymers are selected from groups B, C, and Dwherein

-   -   group A consists of the homopolymer of CH₂═CFCF₃    -   group B consists of copolymers comprising >25 mole % of monomer        units derived from CF₂═CHOR_(f) in combination with monomer        units derived from vinylidene fluoride wherein R_(f) is a linear        or branched C1 to C6 fluoroalkyl radical having the formula        C_(n)F_(2n−y+1)H_(y) wherein the number of hydrogens is less        than or equal to the number of fluorines, no more than two        adjacent carbons atoms are bonded to hydrogens, and either        oxygen can replace one or more of the carbons providing at least        one of the carbons adjacent to any ether oxygen is        perfluorinated;    -   group C consists of copolymers comprising >10 mole % of monomer        units derived from CH₂═CFCF₃, CF₂═CHOR_(f), or a mixture thereof        in combination with monomer unit derived from 1,3        perfluorodioxoles wherein R_(f) is a linear or branched C1 to C6        fluoroalkyl radical having the formula C_(n)F_(2n−y+1)H_(y)        wherein the number of hydrogens is less than or equal to the        number of fluorines, no more than two adjacent carbons atoms are        bonded to hydrogens, and ether oxygen can replace one or more of        the carbons providing at least one of the carbons adjacent to        any oxygen is perfluorinated, and wherein said        1,3-perfluorodioxole has the structure

wherein R_(a) and R_(b) are independently F or linear —C_(n)F_(2n+1),optionally substituted by ether oxygen, for which n=1 to 5.

group D consists of copolymers comprising 40 to 60 mole % of monomerunits derived from a monomer represented by the formula

in combination with monomer units derived from vinylidene fluoride andor vinyl fluoride wherein G and Q are independently F (but not both F),H, R_(f), or —OR_(f) wherein R_(f) is a linear or branched C1 to C5fluoroalkyl radical having the formula C_(n)F_(2n−y+1)H_(y) wherein thenumber of hydrogens is less then or equal to the number of fluorines, nomore than two adjacent carbons atoms are bonded to hydrogens, and etheroxygen can replace one or more of the carbons providing that at leastone of the carbons adjacent to any ether oxygen is perfluorinated.

The polymers suitable for the practice of the present invention areuseful in the manufacture of transmissive and reflective opticalelements, such as lenses and beam splitters mirrors and etalons, for usein the vacuum UV region.

The polymers suitable for the present invention may also be used aselements in a compound lens designed to reduce chromatic aberrations. Atpresent only CaF₂ and possibly hydroxyl free silica are viewed as havingsufficient transparency at 157 nm to be used in transmissive focussingelements. It is also commonly known (e.g. see R. Kingslake, AcademicPress, Inc., 1978, Lens Design Fundamentals, p. 77) that by using asecond material of different refractive index and dispersion, anachromatic lens can be created. Thus, by using one of these materials inconjunction with CaF₂, it is expected that an achromatic lens can beconstructed from this and other similar materials described in thisapplication.

An additional area in which polymers play a critical role is as thephotosensitive photoresist which captures the optical latent image. Inthe case of photoresists, light must penetrate the full thickness of theresist layer for a latent optical image, with well defined vertical sidewalls to be produced during optical imaging which then will produce thedesired resist image in the developed polymer. When used as a resist at157 nm, a polymer can have a considerably higher absorption coefficientof A<˜2-3 per micrometer of film thickness, if the resist thickness islimited to about 2000 Å.

As used herein, the term amorphous fluoropolymer means a fluoropolymerthat exhibits no melting point when analyzed by Differential ScanningCalorimetry. No melting point means no melting associated thermal eventof greater than 1 Joule/gram.

Listing a monomer as a precursor to transparent polymers is not meant toimply that it will either homopolymerize or form a copolymer with anyother listed monomer. Hexafluoroisobutylene for example, does not formuseful homopolymer or copolymerize with tetrafluoroethylene underordinary conditions. While these materials are being claimed for use at150 to 260 nm, they also make excellent clear polymers at longerwavelengths, up to 800 nm, and may also be suitable for someapplications at still shorter wavelengths.

Syntheses of R₁R₂C═CH₂ monomers are well known in the art. R₁═CF₃,R₂═C₂F₅ has been made by treating2-trifluoromethyl-3-chloro-4,4,4-trifluoro-2-butenyl p-toluenesulfonatewith KF Ltd.).(Japanese Patent Application JP 95-235253). R₁═R₂═CF₂H hasbeen made by treating (HCF₂)₂C(OH)Me with SF₄(U.S. Pat. No. 3,655,788).R₁═CF₃, R₂═CF₂H and R₁═R₂═CF₂Cl have been made by reacting thecorresponding fluoroalcohol R₁C(OH)MeR₂ with PCI₆ (German Patent1945614), R₁R₂C═CH₂ can also be made by methods developed forhexafluoroisobutylene such as heating (CF₃)₂CMeCOF with metal halides(Japanese Patent Application JP 93-312470), by reacting (CF₃)₂CHCOOMewith HCHO in the presence of amines (Japanese Patent Application JP86-52298), by reacting hexafluoroacetone with acetic anhydride at hightemperatures (U.S. Pat. No. 3,894,097, Allied Corp. USA), by thereaction of (CF₃)₂C(OH)₂ with acetic anhydride at high temperatures(German Patent Application DE 84-3425907), and by the reaction of(CF3)2CHCH2OH with base (S. Misaki, S. Takamatsu, J. Fluorine Chem.,24(4), 531-3 (1984). In one embodiment of the invention are employedcopolymers of CF2═CHORf with vinylidene fluoride (VF2) andperfluoro-1,3-dioxoles where Rf is defined as a linear or branched C1 toC6 C_(n)F_(2n−y+1)H_(y) group in which the number of hydrogens is lessthan or equal to the number of fluorines, no more than two adjacentcarbons atoms are bonded to hydrogens, and ether oxygen can replace oneor more of the carbons providing at least one of the carbons adjacent toany ether oxygen is perfluorinated. The monomers can be present in anyratio as long as the content of VF2 is not so high as to introducecrystallinity (more than about 75% VF2) or the PDD content so high as tomake for low solubility (more than about 90% PDD).

Monomers such as vinylidene fluoride, PDD, and2,3,3,3-tetrafluoropropene-1 are items of commerce either as puremonomers or incorporated in commercial polymers. Numerous substitutedperfluoro-1,3-dioxoles are described in J. Sheirs, editor, ModernFluoropolymers, John Wiley and Sons, West Sussex, England, 1997, p. 400.Monomers CF2═CHORA where RA is a linear or branched C2 to C20 carbongroup substituted with H, F, and other elements has been reported inU.S. Pat. No. 6,300,526B1, along with a general synthetic method thatinvolves the reaction of a 2-halo-2,2-difluoroethylic alcohol with aflorinated olefin in the presence of an alkaline or alkaline earthhydroxide followed by dehydrohalogenation. The monomer CF2═CHOCF2CF2Hwas made by reacting TFE with ClCF2CH2OH and KOH to give the

ClCF2CH2OCF2CF2H adduct which was then dehydrochlorinated with base andheat. CF3OCH═CF2 has been reported by Paul D. Schuman, Sci. Tech.Aerospace Rept. 1966, 4 (6), N66-15770. Higher homologs RfOCH═CF2 inwhich Rf is a perfluoroalkyl group should be available by combining thehypofluorite/dehydrohalogenation chemistries in EP 0683 181 A1 withNavarrini, et al., J. Fluorine Chem., 95, 27(1999). An alternativemethod of making RfOCH═CF2 was developed here to avoid the difficultiesof making and working with hypofluorites: ester formation, fluorinationwith SF4, and dehydrohalogenation.

2,3,3,3-tetrafluoropropene-1 homopolymer has been reported (D. Brown, L.Wall, Polym. Prepr., Amer. Chem. Soc., Div. Polym. Chem. 1971, 12, 1,pgs. 302-304) and 2,3,3,3-tetrafluoropropene has been reported tocopolymerize with a variety of other fluorocarbon and hydrocarbonmonomers (U.S. Pat. No. 5,637,663, JP 09288915 A2 19971104).

The starting material for the CH2═C(CF3)CF2OR family of monomers ishexafluoroisobutylene fluorosulfate,

CH2═C(CF3)CF2OSO2F. Hexafluoroisobutylene fluorosulfate is made by thereaction of hexafluoroisobutylene with sulfur trioxide in the presenceof B(OC2H5)3 catalyst. Alkoxide anions RO— can then be used to displacethe fluorosulfate group in hexafluoroisobutylene fluorosulfate givingthe desired CH2═C(CF3)CF2OR monomers. This chemistry can be run in dry,aprotic solvents that support alkoxide anion formation and that dissolvethe hexafluoroisobutyene fluorosulfate. Possible solvents includediethylene glycol dimethyl ether, tetramethylene sulfone, andacetonitrile with diethyleneglycol dimethyl ether being preferred.Reaction temperatures range from −50° C. to 100° C. A preferred reactiontemperature is from −25 to +25° C., preferably from −15 to −5° C. Whilehydrocarbon, fluorohydrocarbon, or fluorocarbon alkoxides can be usedfor the displacement of the fluorosulfate group, high UV transparencyresults when R is a linear or branched C1 to C6 fluoroalkyl radicalhaving the formula C_(n)F_(2n−y+1)H_(y) wherein the number of hydrogensis less than or equal to the number of fluorines, no more than twoadjacent carbons atoms are bonded to hydrogens, and ether oxygen canreplace one or more of the carbons providing at least one of the carbonsadjacent to any ether oxygen is perfluorinated.Polymers produced from the above monomers may be prepared as follows.Polymer synthesis can be done by any of the nonaqueous or aqueousemulsion techniques well known to fluoroolefin polymerizations. Innonaqueous polymerization, an autoclave is most frequently charged withsolvent, initiator, and monomers. The solvent is typically a fluid thatdoes not interfere with the growing radical chain: this can include neatmonomer, compressed gases such as carbon dioxide, or moreconventionally, fluids such as Vertrel™ XF (CF3CFHCFHCF2CF3), Solkane™365 mfc (CF3CH2CF2CH3). Freon™ 113 (CF2ClCCl2F), perfluorooctane, orFluorinert™ FC-75. A great variety of radical sources are known toinitiate fluorolefin polymerizations including diacyl peroxides, dialkylperoxides, hydroperoxides, peroxyesters, percarbonates, azo compounds,NF3, and highly sterically hindered perfluorocompounds for whichappropriate initiation temperatures vary from ˜0 to 300° C. In the thepresent invention preferred initiators are perfluorodiacylperoxides suchas DP or perfluoropropionyl peroxide. In the case of DP, polymerizationscan be run at 10 to 50° C., more preferably at 20 to 35° C. In the caseof gaseous monomers such as vinylidene fluoride, typically enoughmonomer is added to generate an internal pressure of 50 to 1000 psi atoperating temperature. These polymers can also be made by aqueousemulsion polymerization using initiators such as potassium persulfate orVazoTM 56 WSP [2,2′-]2,2′-azobis(2-amidinopropane)dihydrochloride] inthe presence of surfactant. But the introduction of possiblycontaminating surfactants and end groups can make emulsionpolymerization undesirable for high UV transparency. In the case of theparticular polymers being made here, the CH2═C(CF3)CF2OR content in thefinal polymers should be about 40 to 60 mole % because CH2═C(CF3)CF2ORprefers to alternate and VF2 content should be ˜75 mole % or less sincemore VF2 leads to crystallinity.

EXAMPLES

Abbreviations employed herein include:

HFIB hexafluoroisobutylene

PDD 4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole

DSC Differential scanning calorimetry

H-Galden® ZT 85 A trademark of Ausimont,HCF₂O(CF₂O)_(n)(CF₂CF₂O)_(m)CF₂H

DP: hexafluoropropyleneoxide dimer peroxide of structure

CF₃CF₂CF₂OCF(CF₃)(C═O)OO(C═O)CF(CF₃)OCF₂CF₂CF₃

Novec™ HFE-7500, a product of 3M CF₃CF(CF₃)CF(OC₂H₅)CF₂CF₂CF₃

Vertrel® XF, a product of DuPont, CF₃CFHCFHCF₂CF₃

HFIB Fluorosulfate: CH₂═C(CF₃)CF₂OSO₂F or3,3-dihydro-2-trifluoromethylperfluoroallyl fluorosulfate.

The absorbance/micron of was measured for polymer films spin-coated onto CaF₂ substrates using standard method in the art as described in R.H. French, R. C. Wheland, D. J. Jones, J. N. Hilfiker, R. A. Synowicki,F. C. Zumsteg, J. Feldman, A. E. Feiring, “Fluoropolymers for 157 nmLithography: Optical Properties from VUV Absorbance and EllipsometryMeasurements”, Optical Microlithography XIII, SPIE Vol. 4000, edited byC. J. Progler, 1491-1502 (2000). The VUV transmission of each CaF₂substrate was measured prior to the spin coating of the polymer film.Then the VUV transmission of the polymer film on that particular CaF₂substrate was measured, using a VUV-Vase model VU-302 spectroscopicellipsometer, which is capable of performing transmission measurements,made by J. A. Woollam Inc. (J. A. Woollam Co., Inc. Lincoln, Nebr. Thefilm thickness was determined using a Filmetrics (Filmetrics Inc., SanDiego, Calif. model F20 thin film measurement system. Using Equation 1,the spectral transmission and the film thickness, the values of theabsorbance/micron for the polymers were calculated from 145 nm to longerwavelengths, including at 157, 193, and 248 nm.

Optical properties (index of refraction, “n” and extinction coefficient,“k”) are determined from variable angle spectroscopic ellipsometry(VASE) at three incident angles covering the wavelength range from143-800 nm, corresponding to an energy range of 1.5-8.67 eV. The polymerfilms were spin coated onto a silicon substrate. The VASE ellipsometerwas manufactured by J. A. Woollam Company, 645 M Street, Suite 102,Lincoln, Nebr. 68508 USA. Optical constants were fit to these datasimultaneously, using an optical model of the film on the substrate. Seegenerally, O. S. Heavens, Optical Properties of Thin Solid Films, pp.55-62, Dover, N.Y., 1991.

Example 1 Poly[(CH₂═C(CF₃)CF₂OCH(CF₃)₂/CH₂═CF₂]1

A. Preparation of 1,1,5-trihydro-2,5-bis(trifluoromethyl)-4-oxo-perfluoro-1-hexene,CH₂═C(CF₃)CF₂OCH(CF₃)₂ monomer

A 100 ml flask was charged with tributylamine (15 g), diglyme (15 ml),and hexafluoroisopropanol (13.7 g) in a dry box. HFIB fluorosulfate(20.0 g) was added dropwise at 3-12° C. The resulting mixture wasstirred at room temperature for 2 hours. The mixture was fresh distilledto give a liquid, which was then spinning band distilled to afford 21.1g product, bp 92-3° C., yield 83%. (Less pure fractions were notcounted.) 19 F NMR (CDCl3) −65.3 (t, J=7 Hz, 3 F), −70.8 (m, 2 F), −74.0(q, J=5 Hz, 6 F) ppm. 1 H NMR (CDCl3) 4.99 (septet, J=5 Hz, 1 H), 6.37(m, 2 H) ppm. 13 C NMR (CDCl3) 69.4 (septet, t, J=35.4 Hz), 118.8 (t,J=269 Hz), 120.2(q, J=283 Hz), 120.6 (sextet, J=5 Hz), 130.9 (sextet,J=35 Hz) ppm.

B. CH₂═C(CF₃)CF₂OCH(CF₃)₂ copolymerization with CH₂═CF₂

A 75 ml stainless steel autoclave chilled to <−20° C. was loaded with11.6 g of CH₂═C(CF₃)CF₂OCH(CH₃)₂ monomer, 10 ml of CH₃CH₂CF₂CH₃ solvent,and 10 ml of ˜0.17 M DP in CF₃CFHCFHCF₂CF₃. The autoclave was chilled,evacuated and further loaded with ˜2 g of vinylidene fluoride. Theautoclave was shaken overnight at room temperature. The resulting hazyfluid was dried under nitrogen, then under pump vacuum, and finally for66 hours in a 75° C. vacuum oven, giving 12.9 g of white polymer.Fluorine NMR in hexafluorobenzene found 53.4 mole % vinylidene fluorideand 46.6 mole % CH₂═C(CF₃)CF₂OCH(CF₃)₂. Inherent viscosity inhexafluorobenzene at 25° C. was 0.116 dL/g. A small sample was purifiedfor DSC measurements by dissolving 0.5 g of polymer in 3 g of H GaldenZT 85 solvent [HCF2O(CF2O)m(CF2CF2O)nCF2H], filtering the haze off usinga 0.45 micron PTFE syringe filter (Whatman Autovial®), evaporating offexcess solvent, and drying in a 75° C. vacuum oven for 16 hours. The Tgwas now 47° C. (10° C./min, N₂, second heat).

C. Solution preparation

A hazy solution was made by rolling 2 g of polymer with 18 g of HGalden™ ZT 85 solvent. The haze was removed by filtering first through abed of chromatographic silica in a 0.45 μ glass fiber microfiber syringefilter (Whatman Autovial™), centrifuging at 15000 rpm, and finallyfiltering again through a 0.2 μ PTFE syringe filter (Gelman AcrodiscCR). Evaporation of 0.1192 g of this solution on a glass slide gave aclear film weighing (0.0085 g (solution ˜7 wt % in solids).

D. Optical characterization Spinning of solution:

The polymer solution so prepared was spin coated in an enclosed vaporcan spinner at spin speeds of 800 rpm for 30 seconds, after an initial10 second vapor equilibration period onto CaF2 and silicon substrateswith a subsequent post apply bake at 120 C for 2 minutes to producepolymer films of 9200 angstroms thickness for VUV absorbancemeasurements and of 3523 angstroms thickness for VUV ellipsometrymeasurements. VUV absorbance measurements were then used to determinethe absorbance per micrometer and VUV ellipsometry measurements of thefilms on silicon were used to determine the index of refraction.

Optical Results:

The absorbance in units of inverse micrometers for the polymer film soprepared versus wavelength lambda (λ) in units of nanometers is shown inFIG. 1. The 157 nm absorbance/micrometer determined was0.011/micrometer. The 193 nm absorbance/micrometer determined was−0.002/micrometer. The 248 nm absorbance/micrometer determined was−0.002/micrometer.

The index of refraction for Polymer 1 versus wavelength lambda (λ) inunits of nanometers is shown in FIG. 2. The 157 nm index of refractiondetermined is 1.45. The 193 nm index of refraction determined is 1.40.The 248 nm index of refraction is 1.37.

Example 2 Poly[(CH₂═C(CF₃)CF₂OCF(CF₃)₂/CH₂═CF₂]2

Preparation of1,1-dihydro-2,5-bis(trifluoromethyl)-4-oxo-perfluorohex-1-ene,CH₂-═C(CF₃)CF₂OCF(CF₃)₂ monomer A 250 ml flask was charged with KF (12g) and diglyme (55 ml) in a dry box.

Hexafluoroacetone (40.5 g) was added to the mixture via a dry-icecondenser. The solid was dissolved completely. The HFIB fluorosulfate(49 g) was added dropwise. The resulting mixture was stirred at roomtemperature for 3 hours. The mixture was fresh distilled to give aliquid, which was then spinning band distilled to afford 36.3 g product,bp 84-86° C., yield 55%. (Less pure fractions were not counted.) 19 FNMR (CDCl3) −65.3 (t, J=8 Hz, 3 F), −66.6 (m, 2 F), −81.0 (m, 6 F),−146.4 (t, J=23 Hz, 1 F) ppm. 1 H NMR (CDCl3) 6.39 (m) ppm. 13 C NMR(CDCl3) 101.5 (d&septet, J=269, 38 Hz), 117.7 (qd, J=258, 32 Hz), 118.6(t, J=274 Hz), 127.4 (m), 131.2 (m) ppm.B. CH₂═C(CF₃)CF₂OCF(CF₃)₂ copolymerization with CH₂═CF₂ A 110 mlstainless steel autoclave chilled to <−20° C. was loaded with 26 g ofCH₂═C(CF₃)CF₂OCF(CF₃)₂ monomer, 25 ml of CF₃CFHCFHCF₂CF₃ solvent, and 10ml of ˜0.17 M DP in CF₃CFHCFHCF₂CF₃. The autoclave was chilled,evacuated and further loaded with ˜5 g of vinylidene fluoride. Theautoclave was shaken overnight at room temperature. The resultingviscous fluid was dried under nitrogen, then under pump vacuum, andfinally for 88 hours in a 75° C. vacuum oven, given 26.7 g of whitepolymer. Fluoride NMR run in hexafluorobenzene found 51 mole %CH₂═C(CF₃)CF₂OCF(CF₃)₂ and 49 mole % CH₂═CF₂.

DSC, 10° C./min, N₂, 2nd heat neither Tg nor Tm detected InherentViscosity, hexafluorobenzene, 25° C.: 0.083

C. Solution preparation

A clear, colorless solution was made by rolling 2 g of polymer with 18 gof H Galden™ ZT 85 solvent and passing through a 0.45 μ glass fibermicrofiber syringe filter (Whatman Autovial™)

D. Optical characterization

Spinning of solution:

The polymer solution so prepared was spin coated in a conventionalatmosphere spinner at spin speeds of 90 rpm for the absorbance sampleand 500 rpm for the ellipsometry sample for 30 seconds onto CaF2 andsilicon substrates with a subsequent post apply bake at 120 C for 2minutes to produce polymer films of 10800 angstroms thickness for VUVabsorbance measurements and of 3757 angstroms thickness for VUVellipsometry measurements. VUV absorbance measurements of the films onCaF₂ were then used to determine the absorbance per micrometer and VUVellipsometry measurements of the films on silicon were used to determinethe index of refraction.

Optical results:

The absorbance in units of inverse micrometers for the polymer film soprepared versus wavelength lambda (λ) in units of nanometers is shown inFIG. 2. The 157 nm absorbance/micrometer determined was0.0275/micrometer. The 193 nm absorbance/micrometer determined was0.0045/micrometer. The 248 nm absorbance/micrometer determined was0.008/micrometer.

The index of refraction for Polymer 2 versus wavelength lambda (λ) inunits of nanometers is shown in FIG. 4. The 157 nm index of refractiondetermined is 1.44. The 193 nm index of refraction determined is 1.39.The 248 nm index of refraction is 1.37.

Example 3 Poly(CF₂═CHOCF₂CF₂H/CH₂═CF₂) 3

A. Preparation of 1, 1,2,2-tetrafluoroethyl 2,2-difluorovinyl ether,CF₂═CHOCF₂CF₂CF₂H monomer.

a/Preparation of 1,1,2,2-Tetrafluoroethyl 2-chloro-2,2-difluoroethylether

A mixture of 2-chloro-2,2-difluoroethanol (22.0 g), t-butanol (45 ml),KOH (10.0 g) and TFE (25 g) was shaken at room temperature for 8 hoursin a autoclave. The bottom layer of the reaction mixture was isolatedand washed with water (40 ml) to give a crude product,1,1,2,2-Tetrafluoroethyl 2-chloro-2,2-difluoroethyl ether, 29.5 g, yield72%. This product was used for next step without further purification.

b/Preparation of 1,1,2,2-Tetrafluoroethyl 2,2-difluorovinyl ether Amixture of 1,1,2,2-Tetrafluoroethyl 2-chloro-2,2-difluoroethyl ether(29.0 g), KOH (10.0 g), and DMSO (5 ml) was heated to reflux on aspinning band distillation apparatus. The product was distilled out togive 9.6 g of 1,1,2,2-Tetrafluoroethyl 2,2-difluorovinyl ether, bp 38°C., yield 40%.

19 F NMR (CDCl3) −92.3 (s, 2 F), −92.7 (ddt, J=57, 14, 3 Hz, 1 F),−110.5 (dd, J=54, 3 Hz, 1 F), −137.4 (dt, J=52, 5 Hz. 2 F) ppm, 13 C NMR(CDCl3) 98.9 (dd, J=61, 16 Hz), 107.2 (tt, J=252, 40 Hz), 116.3 (tt,J=273, 40 Hz) 157.0 (dd, J=293, 281 Hz) ppm. 1 H NMR (CDCl3) 5.84 (tt,J=52, 3 Hz, 1 H), 6.10 (dd, J=13, 4 Hz, 1 H) ppm.

B. CF₂═CHOCF₂CF₂H copolymerization with CH₂═CF₂ A 75 ml stainless steelautoclave chilled to <20° C. was loaded with 9.4 g of CF₂═CHOCF₂CF₂Hmonomer, 10 ml of CF₃CFHCFHCF₂CF₃ solvent, and 5 ml of ˜0.17 M DP inCF₃CFHCFHCF₂CF₃. The autoclave was chilled, evacuated and further loadedwith ˜4 g of vinylidene fluoride. The autoclave was shaken overnight atroom temperature. The resulting hazy fluid was dried under nitrogen,then under pump vacuum, and finally for 23 hours in a 77° C. vacuumoven, giving 4.6 g of tacky gum.

Calc. for (C₂H₂F₂)₃(C₄H₂F₆O)₂: 30.45% C 1.83% H

Found: 30.65% C 1.41% H

DSC, 10° C./min, N₂, 2nd heat Tg@−11° C.

Inherent Viscosity, acetone, 25° C.: 0.122

C. Solution preparation

A clear, colorless solution was made by rolling 2.5 g of polymer with 10g of 2-heptanone solvent and passing through a 0.45μ glass fibermicrofiber syringe filter (Whatman Autovial™).

D. Optical characterization Spinning of solution:

The polymer solution so prepared was spin coated in a conventionalatmosphere spinner at spin speeds of 1000 rpm for 60 seconds onto CaF2and silicon substrates with a subsequent bake at 120 C for 2 minutes toproduce polymer films of 900 angstroms thickness .VUV absorbancemeasurements were then used to determine the absorbance per micrometerand VUV ellipsometry measurements of the films on silicon were used todetermine the index of refraction.

The absorbance in units of inverse micrometers for the polymer film soprepared versus wavelength lambda (λ) in units of nanometers is shown inFIG. 5. The 157 nm absorbance/micrometer determined was−0.002/micrometer. The 193 nm absorbance/micrometer determined was−0.001/micrometer. The 248 nm absorbance/micrometer determined was0.003/micrometer.

The index of refraction versus wavelength lambda (λ) in units ofnanometers was shown in FIG. 6. The 157 nm index of refractiondetermined was 1.48. The 193 nm index of refraction determined was 1.42.The 248 nm index of refraction was 1.39.

Example 4 Poly(CF₂═CHOCH₂CF₂H/PDD) 4

A. CF₂═CHOCF₂CF₂H copolymerization with PDD

A ˜30 ml glass sample vial containing a magnetic stir bar was cappedwith a rubber septum, flushed with nitrogen, and chilled on dry ice. Thesample vial was then injected with 5 g of CF₂═CHOCF₂CF₂H monomer, 6.8 gof PDD monomer, and 1 ml of ˜0.17 M DP in CF₃CFHCFHCF₂CF₃. Afterflushing the vial once again with nitrogen, the contents of the vialwere allowed to warm slowly to room temperature with magnetic stirring.By the next morning the reaction mixture was hazy and viscous. Another 1ml of ˜0.17 M DP in CF₃CFHCFHCF₂CF₃ was injected and the reactionmixture stirred another 4 days at room temperature. The contents of thevial were poured into ˜125 ml of hexane and the precipitate isolated byvacuum filtration giving 8.6 g of crumbly white solid.

Calc. for (C₄F₆OH₂)₁(C₅F₈O₂)₂: 25.17% C 0.30% H

Found: 24.97% C 0.56% H

DSC, 10° C./min, N₂, 2nd heat Tg@25° C.

Inherent Viscosity, hexafluorobenzene, 25° C.: 0.126

C. Solution preparation

A clear, colorless solution was made by rolling 2.5 g of polymer with 10g of Novec™ HFE-7500 solvent and passing through a 0.45μ glass fibermicrofiber syringe filter (Whatman Autovial™).

D. Optical characterization The polymer solution so prepared was spincoated in a conventional atmosphere spinner at spin speeds of 2000 rpmfor the absorbance sample and 800 rpm for the ellipsometry sample for 30seconds onto CaF2 and silicon substrates with a subsequent post applybake at 120 C for 2 minutes to produce polymer films of 11200 angstromsthickness for VUV absorbance measurements and of 6272 angstromsthickness for VUV ellipsometry measurements. VUV absorbance measurementsof the films on CaF₂ were then used to determine the absorbance permicrometer and VUV ellipsometry measurements of the films on siliconwere used to determine the index of refraction.

The 157 nm absorbance/micrometer determined was 0.055/micrometer. The193 nm absorbance/micrometer determined was 0.014/micrometer. The 248 nmabsorbance/micrometer determined was 0.008/micrometer.

The 157 nm index of refraction determined was 1.41. The 193 nm index ofrefraction determined was 1.36. The 248 nm index of refraction was 1.35.

Example 5 Poly(CF₂═CHOCF₂CF₂CF₃/CH₂═CF₂) 5

A. Preparation of perfluoroethyl 2,2-difluorovinyl ether, CF₂═CHOCF₂CF₃monomer.

a) Preparation of 2-chloro-2,2-difluoroethyl trifluoroacetate.

A mixture of 2-chloro-2,2-difluoroethanol (132 g) and DMF (15 drops) wascharged to a 250 ml flask. Trifluoroacetyl chloride (17 g) wasintroduced to the flask via a dry ice condenser at about 50° C. Theresulting mixture was refluxed for 4 hours. The mixture was distilled togive 234 g of the acetate, bp 79-81° C., yield 97%. 19 F NMR (CDCl3)−62.8 (t, J=8 Hz, 2 F), −75.2 (s, 3 F) ppm, 1 H NMR (CDCl3) 4.79 (t, J=9Hz) ppm.

b) Preparation of perfluoroethyl 2-chloro-2,2-difluoroethyl ether.

A mixture of 2-chloro-2,2-difluoroethyl trifluoroacetate (20 g), HF (150g), and SF₄ (60 g) was heated to 150° C. for 21 hours. The mixture waspoured into water (300 ml). The bottom layer was isolated to give crudeproduct (16.1 g), yield 73%. It was relatively pure based on NMRanalysis. Then the crude product was washed with Na2CO3 until pH=8,dried over Na2SO4, and distilled to afford the product, 11 g, bp 54-55°C., yield 50%. 19 F NMR (CDCl3) −63.5 (tt, J=9, 3 Hz, 2 F), −86.4 (s, 3F), −91.2 (s, 2 F) ppm.

c) Preparation of Perfluoroethyl 2,2-difluorovinyl ether

A mixture of perfluoroethyl 2-chloro-2,2-difluoroethyl ether (69 g), KOH(30.0 g) and DMSO (15 ml) was heated to reflux on a spinning banddistillation apparatus. The product was distilled out to give 43 g ofperfluoroethyl 2,2-2,2-difluorovinyl ether, bp 15° C., yield 85%. 19 FNMR (CDCl3) −86.5 (s, 3 F), −91.8 (dd, J=18, 4 Hz, 1 F), −92.1 (s, 2 F),−109.3 (d, J=18 Hz, 1 F) ppm. 1 H NMR (CDCl3) 6.08 (dd, J=13, 4 Hz) ppm.13 C NMR (CDCl3) 98.9 (m), (ddt, J=62, 16, 5 Hz), 116.2 (qt, J=284, 45Hz), 114.3 (tq, J=275, 42 Hz), 156.3 (d, J 295 Hz) ppm.

B. Copolymerization of CF₂═CHOCF₂CF₃ with CH₂═CF₂

A 75 ml stainless steel autoclave chilled to <−20° C. was loaded with 10ml of CF₃CFHCFHCF₂CF₃ solvent and 5 ml of ˜0.17 M DP in CF₃CFHCFHCF₂CF₃.The autoclave was chilled, evacuated and further loaded with 10 g ofCF₂═CHOCF₂CF₃ and ˜4 g of vinylidene fluoride. The autoclave was shakenovernight at room temperature. The resulting fluid was dried undernitrogen, then under pump vacuum, and finally for 4 days in a 77° C.vacuum oven, giving 2.6 g of tacky gum.

Calc. for (C₄F₇OH)₁₀(C₂H₂F₂)₁₁: 27.74% C 1.20% H

Found: 27.89% C 0.91% H

DSC, 10° C./min, N₂, 2nd heat Tg@−5° C.

C. Solution preparation A solution was made by rolling 1 g of polymerwith 9 g of H Galden™ ZT 85 solvent and passing through a 0.45μ PTFEfiber microfiber syringe filter (Whatman Autovial™) to remove haze.

D. Optical characterization

The polymer solution so prepared was spin coated in a conventionalatmosphere spinner at spin speeds of 1000 rpm for the absorbance sampleand 800 rpm for the ellipsometry sample for 30 seconds onto CaF2 andsilicon substrates with a subsequent post apply bake at 120 C for 2minutes to produce polymer films of 10200 angstroms thickness for VUVabsorbance measurements and of 5880 angstroms thickness for VUVellipsometry measurements. VUV absorbance measurements of the films onCaF₂ were then used to determine the absorbance per micrometer and VUVellipsometry measurements of the films on silicon were used to determinethe index of refraction.

The 157 nm absorbance/micrometer determined was 0.034/micrometer. The193 nm absorbance/micrometer determined was 0.02/micrometer. The 248 nmabsorbance/micrometer determined was 0.01/micrometer.

The 157 nm index of refraction determined was 1.47. The 193 nm index ofrefraction determined was 1.40. The 248 nm index of refraction was 1.38.

Example 6 Poly(CF₂═CHOCF₂CF₂CF₂CF₃/PDD) 6

A. Preparation of perfluorobutyl 2,2-difluorovinyl ether.

CF₂═CHOCF₂CF₂CF₂CF₃ monomer.

a) Preparation of 2-chloro-2,2-difluoroethyl perfluorobutyrate.

A 100 ml flask was charged with 2-chloro-2,2-difluoroethanol (49 g) andDMF (10 drops). Perfluorobutyryl chloride (100 g) was added to the flaskdropwise at about 50° C. The resulting mixture was heated at 50° C. foranother 3 hours. The mixture gave 115 g of product, bp 128-130° C.,yield 88%.

b) Preparation of perfluorobutyl 2-chloro-2,2-difluoroethyl ether. Amixture of 2-chloro-2,2-difluoroethyl perfluorobutyrate (90 g), HF (500g), and SF₄ (150 g) was heated to 110° C. for 40 hours in an autoclave.Water (500 ml) was added to the reactor at 0° C. The bottom layer wasisolated and dried over MgSO4, and distilled to afford the product, 71g, bp 98° C., yield 74%, 19 F NMR (CDCl3) −63.5 (tt, J=10, 3 Hz, 2 F),−81.6 (t, J=10 Hz, 3 F), −86.2 (s, 2 F), 126.6 (m, 2 F), 127.1 (m, 2 F)ppm. 1 H NMR (CDCl3) 4.42 (t, J=10 Hz) ppm.

c) Preparation of Perfluorobutyl 2,2-difluorovinyl ether.

A mixture of perfluorobutyl 2-chloro-2,2-difluoroethyl ether (42.2 g),KOH (50.0 g) and DMSO (0.5 ml) was heated to distill the product bp <68°C. The product was redistilled to give 30.8 g of perfluorobutyl2,2-difluorovinyl ether, bp 65° C., yield 82%. 19 F NMR (CDCl3) −81.5(t, J=10 Hz, 3 F), −86.8 (s, 2 F), −91.0 (ddt, J=52, 13, 3 Hz, 1 F),−108.7 (dd, J=52.4 Hz, 1 F), −126.6 (m, 2 F), −127.1 (m, 2 F) ppm. 1 HNMR (CDCl3) 6.14 (dd, J=13, 4 Hz) ppm.

B. CF₂═CHOCF₂CF₂CF₂CF₂CF₃ copolymerization with PDD

A ˜30 ml glass sample vial containing a magnetic stir bar and 5 ml ofCF₃CFHCFHCF₂CF₃ was capped with a rubber septum, flushed with nitrogen,and chilled on dry ice. The sample vial was injected with 6 g ofCF₂═CHOCF₂CF₂CF₂CF₃ monomer, 4.88 g of PDD monomer, and 1 ml of ˜0.17 MDP in CF₃CFHCFHCF₂CF₃, purging the vial with nitrogen after eachaddition. The contents of the vial were allowed to warm slowly to roomtemperature with magnetic stirring. By the next morning the reactionmixture was a thick gel. The contents of the vial were poured into ˜125ml of hexane and the lumpy precipitate isolated by decantation. The wetpolymer was dried by nitrogen purging, putting under pump vacuum, andfinally heating for 24 hours in a 80° C. vacuum oven. This gave 6.15 gof white lumps. Fluorine NMR found 77.5 mole % PPD and 22.5 mole %CF₂═CHOCF₂CF₂CF₂CF₃.

DSC, 10° C./min, N₂, 2nd heat. Neither Tg, nor Tm detected.

C. Solution preparation

A clear, colorless solution was made by rolling 1 g of polymer with 9 gof Novec™ HFE-7500 solvent for about 5 days and passing through a 0.45μglass fiber microfiber syringe filter (Whatman Autovial™).

D. Optical characterization The polymer solution so prepared was spincoated in a conventional atmosphere spinner at spin speeds of 2000 rpmfor 30 seconds onto CaF2 and silicon substrates with a subsequent postapply bake at 120 C for 2 minutes to produce polymer films of 11700angstroms thickness for VUV absorbance measurements and of 11492angstroms thickness for VUV ellipsometry measurements. VUV absorbancemeasurements of the films on CaF₂ were then used to determine theabsorbance per micrometer and VUV ellipsometry measurements of the filmson silicon were used to determine the index of refraction.

The 157 nm absorbance/micrometer determined was 0.022/micrometer. The193 nm absorbance/micrometer determined was 0.0015/micrometer. The 248nm absorbance/micrometer determined was −0.001/micrometer.

The 157 nm index of refraction determined was 1.35. The 193 nm index ofrefraction determined was 1.30. The 248 nm index of refraction was 1.28.

Example 7 Poly(CH₂═CFCF₃)7

A. Homopolymerization of 2,3,3,3-Tetrafluoropropene-1

A 75 ml autoclave chilled to <−20° C. was loaded with 10 ml of ˜0.17 MDP in CF₃CFHCFHCF₂CF₃ solvent and 10 g of 2,3,3,3-tetrafluoropropene-1.The reaction mixture was shaken overnight. The resulting solution wasevaporated down under nitrogen, then for 24 hours under pump vacuum, andfinally for 45 hours in a 75° C. vacuum oven. This gave 1.77 g ofpolymer.

-   -   DSC, 10° C./min, N₂, second heat Tg@39° C.    -   Inherent viscosity, acetone, 25° C. 0.029 dL/g        B. Solution Preparation

A solution was made by rolling 1.17 g of polymer with 10.53 g of HGalden ZT 85 and filtering through a 0.45μ glass fiber microfibersyringe filter (Whatman Autovial™).

C. Optical Characterization

Solutions of Polymer 7 were spin coated in a conventional atmospherespinner at spin speeds of 2000 rpm for the absorbance sample and 800 rpmfor the ellipsometry sample for 30 seconds onto CaF₂ and siliconsubstrates with a subsequent post apply bake at 120 C for 2 minutes toproduce polymer films of 7000 angstroms thickness for VUV absorbancemeasurements and of 909 angstroms thickness for VUV ellipsometrymeasurements. VUV absorbance measurements of the films on CaF₂ were thenused to determine absorbance per micrometer and VUV ellipsometrymeasurements of the films on silicon were used to determine the index ofrefraction.

Optical results:

The 157 nm absorbance/micrometer determined is 0.005/micrometer. The 193nm absorbance/micrometer determined is 0.007/micrometer. The 248 nmabsorbance/micrometer determined is 0.01/micrometer.

The 157 nm index of refraction determined is 1.47. The 193 nm index ofrefraction determined is 1.42. The 248 nm index of refraction is 1.38.

Example 8 Poly(CH2═CFCF3/PDD) 8

A. Copolymerization of 2,3,3,3-tetrafluoropropene-1 withperfluoro-dimethyldioxole

A 75 ml autoclave chilled to <−20° C. was loaded with 5 ml of ˜0.17 M DPin CF3CFHCFHCF2CF3 solvent, 12 g of perfluorodimethyldioxole, 10 ml ofCF3CFHCFHCF2CF3 VertrelTM XF), and 11 g of 2,3,3,3-tetrafluoropropene-1.The reaction mixture was shaken overnight at room temperature. Theresulting solution was evaporated down under nitrogen, put under pumpvacuum for 3 days, and then finished by heating for 24 hours in a 75° C.vacuum oven. This gave 3.29 g of white lumps.

Calc. for (C3H2F4)5(C5F8O2)2: 28.37% C

0.95% H

Found: 28.27% C

0.99% H

Inherent viscosity, hexafluorobenzene,25° C. 0.042

B. Solution preparation (Wheland E101100-54)

A solution was made by rolling 2.5 g of polymer with 10 g of H Galden ZT85 and filtering through a 0.45 micron glass microfiber syringe filter(Whatman AutovialTM).

Optical characterization Spinning of solution:

Solutions of Polymer 8 were spin coated in a conventional atmospherespinner at spin speeds of 2000 rpm for the absorbance sample and 800 rpmfor the ellipsometry sample for 30 seconds onto CaF₂ and siliconsubstrates with a subsequent post apply bake at 120 C for 2 minutes toproduce polymer films of 10200 angstroms thickness for VUV absorbancemeasurements and of 3583 angstroms thickness for VUV ellipsometrymeasurements. VUV absorbance measurements of the films on CaF₂ were thenused to determine the absorbance per micrometer and VUV ellipsometrymeasurements of the films on silicon were used to determine the index ofrefraction.

Optical results:

The 157 nm absorbance/micrometer determined is 0.006/micrometer. The 193nm absorbance/micrometer determined is 0.004/micrometer. The 248 nmabsorbance/micrometer determined is −0.004/micrometer.

The 157 nm index of refraction determined is 1.46. The 193 nm index ofrefraction determined is 1.41. The 248 nm index of refraction is 1.38.

1. A method comprising causing a source to emit electromagneticradiation in the wavelength range from 150 nanometers to 260 nanometers;disposing a target surface in the path of at least a portion of saidelectromagnetic radiation in such a manner that at least a portion ofsaid target surface will be thereby illuminated; and, interposing in thepath of at least a portion of said electromagnetic radiation betweensaid target surface and said source a shaped article comprising afluoropolymer exhibiting an absorbance/micrometer ≦1 at wavelengths from150 to 260 nm and a heat of fusion of <1 J/g said fluoropolymer being ahomopolymer selected from group A or copolymers from groups B, C, and Dwherein group A consists of the homopolymer of CH₂═CFCF₃ group Bconsists of copolymers comprising >25 mole % of monomer units derivedfrom CF₂═CHOR_(f) in combination with monomer units derived fromvinylidene fluoride wherein R_(f) is a linear or branched C1 to C6fluoroalkyl radical having the formula C_(n)F_(2n−y+1)H_(y) wherein thenumber of hydrogens is less than or equal to the number of fluorines, nomore than two adjacent carbons atoms are bonded to hydrogens, and etheroxygen can replace one or more of the carbons providing at least one ofthe carbons adjacent to any ether oxygen is perfluorinated; group Cconsists of copolymers comprising >10 mole % of monomer units derivedfrom CH₂═CFCF₃, CF₂═CHOR_(f), or a mixture thereof in combination withmonomer unit derived from 1,3-perfluorodioxoles wherein R_(f) is alinear or branched C1 to C6 fluoroalkyl radical having the formulaC_(n)F_(2n−y+1)H_(y), wherein the number of hydrogens is less than orequal to the number of fluorines, no more than two adjacent carbonsatoms are bonded to hydrogens, and ether oxygen can replace one or moreof the carbons providing at least one of the carbons adjacent to anyoxygen is perfluorinated, and wherein said 1,3-perfluorodioxole has thestructure

wherein R_(a) and R_(b) are independently F or linear —C_(n)F_(2n+1),optionally substituted by ether oxygen, for which n=1 to 5; group Dconsists of copolymers comprising 40 to 60 mole % of monomer unitsderived from a monomer represented by the formula

in combination with monomer units derived from vinylidene fluoride andor vinyl fluoride wherein G and Q are independently F (but not both F),H, R_(f), or —OR_(f) wherein R_(f) is a linear or branched C1 to C5fluoroalkyl radical having the formula C_(n)F_(2n−y+1)H_(y) wherein thenumber of hydrogens is less than or equal to the number of fluorines, nomore than two adjacent carbons atoms are bonded to hydrogens, and etheroxygen can replace one or more of the carbons providing that at leastone of the carbons adjacent to any ether oxygen is perfluorinated. 2.The method of claim 1 wherein the shaped article is a pellicle film foruse in photolithography.
 3. The method of claim 1 wherein said source isa laser emitting 157 nm electromagnetic radiation.
 4. The method ofclaim 1 wherein said target surface comprises a photopolymer.
 5. Themethod of claim 1 wherein said shaped article is a lens and saidfluoropolymer is a coating disposed upon the surface thereof.
 6. Themethod of claim 1 wherein said fluoropolymer is a component of anadhesive composition.
 7. The method of claim 1 wherein said shapedarticle is a lens formed from said fluoropolymer.
 8. The method of claim1 wherein the fluoropolymer is a copolymer of CH₂═C(CF₃)CF₂OCH(CF₃)₂with vinylidene fluoride.
 9. The method of claim 1 wherein thefluoropolymer is a copolymer of CH₂═C(CF₃)CF₂OCF(CF₃)₂ with vinylidenefluoride.
 10. The method of claim 1 wherein the fluoropolymer is acopolymer of CF₂═CHOCF₂CF₂H with vinylidene fluoride.
 11. The method ofclaim 1 wherein the fluoropolymer is a copolymer of CF₂═CHOCF₂CF₂H with4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole.
 12. The method ofclaim 1 wherein the fluoropolymer is a copolymer of CF₂═CHOCF₂CF₃ withvinylidene fluoride.
 13. The method of claim 1 wherein the fluoropolymeris a copolymer of CF₂═CHOCF₂CF₂CF₂CF₃ with4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole.
 14. The method ofclaim 1 wherein the fluoropolymer is a homopolymer of CH₂═CFCF₃.
 15. Themethod of claim 1 wherein the fluoropolymer is a copolymer of CH₂═CFCF₃with 4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole.
 16. An apparatuscomprising an activateable source of electromagnetic radiation in thewavelength range of 150-260 nanometers; and a shaped article comprisinga fluoropolymer exhibiting an absorbance/micron ≦1 at wavelengths from150 to 260 nm and a heat of fusion of <1 J/g said fluoropolymer being ahomopolymer selected from group A or copolymers from groups B, C, and Dwherein group A consists of the homopolymer of CH₂═CFCF₃ group Bconsists of copolymers comprising >25 mole % of monomer units derivedfrom CF₂═CHOR_(f) in combination with monomer units derived fromvinylidene fluoride wherein R_(f) is a linear or branched C1 to C6fluoroalkyl radical having the formula C_(n)F_(2n−y+1)H_(y) wherein thenumber of hydrogens is less than or equal to the number of fluorines, nomore than two adjacent carbons atoms are bonded to hydrogens, and etheroxygen can replace one or more of the carbons providing at least one ofthe carbons adjacent to any ether oxygen is perfluorinated; group Cconsists of copolymers comprising >10 mole % of monomer units derivedfrom CH₂═CFCF₃, CF₂═CHOR_(f), or a mixture thereof in combination withmonomer unit derived from 1,3 perfluorodioxoles wherein R_(f) is alinear or branched C1 to C6 fluoroalkyl radical having the formulaC_(n)F_(2n−y+1)H_(y) wherein the number of hydrogens is less than orequal to the number of fluorines, no more than two adjacent carbonsatoms are bonded to hydrogens, and ether oxygen can replace one or moreof the carbons providing at least one of the carbons adjacent to anyoxygen is perfluorinated, and wherein said 1,3-perfluorodioxole has thestructure

wherein R_(a) and R_(b) are independently F or linear —C_(n)F_(2n+1),optionally substituted by ether oxygen, for which n=1 to 5; group Dconsists of copolymers comprising 40 to 60 mole % of monomer unitsderived from a monomer represented by the formula

within combination with monomer units derived from vinylidene fluorideand or vinyl fluoride wherein G and Q are independently F (but no bothF), H, R_(f), or —OR_(f) where R_(f) is a linear or branched C1 to C5fluoroalkyl radical having the formula C_(n)F_(2n−y+1)H_(y) wherein thenumber of hydrogens is less than or equal to the number of fluorines, nomore than two adjacent carbons atoms are bonded to hydrogens and etheroxygen can replace one or more of the carbons providing that at leastone of the carbons adjacent to any ether oxygen is perfluorinated; saidshaped article being disposed to lie within the optical path of lightemitted from said source when said source is activated.
 17. Theapparatus of claim 16 wherein said activateable light source is a laseremitting 157 nm electromagnetic radiation.
 18. The apparatus of claim 16further comprising a target surface.
 19. The apparatus of claim 18wherein said target surface comprises a photopolymer.
 20. The apparatusof claim 16 wherein said shaped article is a lens and said fluoropolymeris a coating disposed upon the surface thereof.
 21. The apparatus ofclaim 16 wherein said fluoropolymer is a component of an adhesivecomposition.
 22. The apparatus of claim 16 wherein said shaped articleis a lens formed from said fluoropolymer.
 23. The apparatus of claim 16wherein the shaped article is a pellicle film for use inphotolithography.
 24. The apparatus of claim 16 wherein thefluoropolymer is a copolymer of CH₂═C(CF₃)CF₂OCH(CF₃)₂ with vinylidenefluoride.
 25. The apparatus of claim 16 wherein the fluoropolymer is acopolymer of CH₂═C(CF₃)CF₂OCF(CF₃)₂ with vinylidene fluoride.
 26. Theapparatus of claim 16 wherein the fluoropolymer is a copolymer ofCF₂═CHOCF₂CF₂H with vinylidene fluoride.
 27. The apparatus of claim 16wherein the fluoropolymer is a copolymer of CF₂═CHOCF₂CF₂H with4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole.
 28. The apparatus ofclaim 16 wherein the fluoropolymer is a copolymer of CF₂═CHOCF₂CF₃ withvinylidene fluoride.
 29. The apparatus of claim 16 wherein thefluoropolymer is a copolymer of CF₂═CHOCF₂CF₂CF₂CF₃ with4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole.
 30. The apparatus ofclaim 16 wherein the fluoropolymer is a homopolymer of CH₂═CFCF₃. 31.The apparatus of claim 16 wherein the fluoropolymer is a copolymer ofCH₂═CFCF₃ with 4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole.